1. Field of the Invention
The present invention relates to a method of storing characters and figures, and to a photo-typesetting apparatus which projects characters and figures onto a sensitive material using a cathode-ray tube (CRT), laser scanner or other flying spot character imaging device.
2. Description of the Prior Art
In recent years, photo-typesetting machines employing CRT and photo-typesetting machines employing a laser scanner have been developed remarkably and have been widely placed in practical use due to the application of advanced electronics technology. The technical assignment, in this case, is concentrated to how cheaply the characters and figures can be reproduced while maintaining high quality. Generally, however, the system for storing characters and figures consists of digitizing a character to store it as detailedly described below with reference to FIG. 2. To obtain characters of high quality, therefore, they must be digitized or divided into great many number of dots, which contradicts the requirement for cheaply reproducing characters (with reduced memory capacity). From the standpoint of quality, furthermore, there is imposed limitation on the size of the character that is to be reproduced relying upon a predetermined number of dots. When characters of various magnifications are required, characters with different dot numbers must be prepared. In the Japanese language, furthermore, there exist several thousand to ten thousand characters in a single font only, and characters are often used in several fonts. Therefore, to store the characters which are digitized, is not practicable, and various systems for compressing the data have been proposed to cope with the inconvenience. In most of these systems, however, the characters are divided into a predetermined number of dots, and the dots are compressed. Therefore, different data must be stored depending upon the magnification of character, which contradicts the requirement for reducing the memory capacity.
Another system consists of storing the characters and figures in the form of contours. In this system, however, curves are approximated to straight lines. When the data is prepared based upon characters of a predetermined size, therefore, connection points(bending points) of straight line appear on an enlarged scale when larger characters are being treated, and the quality is deteriorated. Conversely, when attempt is made to obtain large characters maintaining high quality, the amount of data to be stored increases proportionately, to offset the meaning of data compression.